Technical Field
This description generally relates to sawmills, and more particularly to optimizers which optimize operation of equipment in sawmills.
Description of the Related Art
The sawmill industry has become largely automated. Full length tree trunks are delivered to sawmills, where they are automatically debarked, scanned and bucked (i.e., cut into log segments) based on their scanned geometry. These log segments are then typically processed at a number of automated stations, depending on the sawmill and the type of wood. These processing stations produce lumber from each log segment, often without any human intervention.
One of the first processing stations in many sawmills is the primary breakdown machine, which processes log segments to produce cants and sideboards. The primary breakdown machine typically includes chip heads for removing slabs as well as one or more band saws for removing sideboards from the log segments, leaving the middle portion of the log which has two flat surfaces and is called a cant. The width of the cant is the width of the lumber that will be sawn from the cant, typically using a gangsaw. A primary breakdown optimizer system may scan each log segment prior to processing at the primary breakdown machine. A primary breakdown optimizer computer of the primary breakdown optimizer system then determines an optimal mix of lumber that can be obtained from that log segment based on the scanned geometry. The optimizer computer may then cause rotation of the log segment and control the relative position of the chip heads and band saws to achieve that optimal mix of lumber.
Downstream from the primary breakdown machine, cants may be further processed at a gangsaw to produce boards. Gangsaws typically include a number of parallel, circular saw blades located at precise intervals within a sawbox and, at the front of the sawbox, two chip heads (e.g., vertical drum chip heads) for removing excess wood from the outside of each cant. Cants may be transported in a straight line through the gangsaw using feed rolls on the upstream and downstream sides of the sawbox. Alternatively, cants may be driven through the gangsaw along a curved path as part of a curve sawing process. Alternatively, the sawbox may be moved during the cut to produce a curved sawing path. In many sawmills, a gangsaw optimizer system employs a cant scanner to scan the incoming cants prior to processing by the gangsaw. A gangsaw optimizer computer of the gangsaw optimizer system then determines optimal locations for the chip heads and saw blades based on the scanned geometry of each cant, including any curved paths for sawing.
Boards sawn by the gangsaw, as well as sideboards from the primary breakdown machine, may then be processed by an edger. The edger typically includes one or more saw blades for sawing along the length of the boards to achieve a chosen width. After edging, the boards are transported to a trimmer, where the boards can be trimmed to a final length. Both the edger and the trimmer may also have corresponding optimization systems including respective scanning systems and optimizer computers to determine how best to saw each piece of lumber.
At each processing station, an optimizer system makes determinations regarding the optimal way to saw each piece to maximize the value and volume of lumber produced from the raw logs. These optimizer systems are very complicated and expensive, and are also difficult to manage properly because of their complexity. If some portion of an optimizer system is not performing as expected, the sawmill can easily suffer a 1% to 4% loss of value until the problem is found and fixed. Thus, significant sums of money may be lost should any one optimizer system not function correctly.
Typically, a cant optimizer has a user interface that displays graphical representations of the cant along with pictures of the boards that will be cut from the particular cant. The sawmill can hypothetically manually review their processes by looking at the computed solutions as presented via the user interface, and manually comparing the actual lumber produced to the lumber that has been predicted by the optimization system. This process is difficult in practice due in part to the large volume of information. This process is also difficult in practice because the outside boards with wane on them generally fall wane side down on the outfeed conveyor, making it hard to judge the width and length of the boards without pulling the boards off of the conveyor downstream. Thus, to the extent that sawmills wish to review their processes, as a practical matter such would have to occur during periods when the sawmill is not running full production, testing individual cants one at a time and collecting the data by hand. This sampling is not only laborious, but does not provide a complete picture of the processes. Further, since the sampling would typically need to occur when the sawmill is not operating at capacity, the results of the sampling would be inherently suspect. This approach certainly cannot provide real time information, nor can this approach provide the ability to assess trends over time.
Thus, modern sawmills lack an effective way to determine if the processing stations are indeed functioning correctly and realizing optimal value from the raw resources. Consequently, there is a need for improvement.